The invention relates to building materials, and, more particularly, to a system for making lightweight blocks formed of aerated concrete.
Autoclaved aerated concrete is a high-quality, load-bearing, as well as insulating building material produced in a wide range of product sizes and strengths. The material has been used successfully in Europe and is now among widely used wall building materials in Europe with increasing market shares in other countries. Aerated concrete is a steam cured mixture of sand or pulverized fuel ash, cement, lime and an aeration agent. High pressure steam curing in an autoclave produces a physically and chemically stable product with an average density being about one fifth that of normal concrete. The material includes no-connecting air cells, and this gives aerated concrete some of it its unique and advantageous properties. Aerated concrete enjoys good strength, low weight, good thermal insulation properties, good sound deadening properties, and has a high resistance to fire.
Aerated concrete may be used in panels or individual building blocks. It has been used for residences; commercial, industrial and agricultural buildings; schools; hospitals; etc. and is a good material in most all climates. Panels or blocks may be joined together using common mortar or thin set glue mortar or adhesive. Aerated concrete has durability similar to conventional concrete or stone and a workability perhaps better than wood. The material can be cut or sawn and readily receives expandable fasteners. Aerated concrete has a thermal conductivity six to ten times better than conventional concrete. The material is also non-rotting, non-toxic and resistant to termites.
As disclosed in U.S. Pat. No. 4,902,211 to Svanholm, for example, aerated concrete may typically be produced as follows. One or several silica containing materials, such as sand, shale ashes or similar materials, as well as one or more calcareous binders, such as lime and/or cement, are mixed with a rising or aeration agent. The aeration agent typically includes aluminum powder which reacts with water to develop hydrogen gas at the same time a mass of what can be considered a calcium silicate hydrate forms. The development of hydrogen gas gives the mass macroporosity. The rising mass is typically contained within a mold. After rising, the mass is permitted to stiffen in the mold forming a semiplastic body which has low strength, but which will keep together after removal from the mold.
After a desired degree of stiffness is achieved and the body is removed from the mold, the body may typically be divided or cut by wires into separate elements having the desired shape, such as building blocks or larger building panels. The divided body is positioned in an autoclave where it is steam cured at high pressure and high temperature to obtain suitable strength. The body is then advanced to a separation station where the adjacent building blocks or panels are separated from one another. The blocks are packaged, such as onto pallets for storage and transportation.
Because the building blocks are divided from the solid mass of material, the blocks are solid generally rectangular bodies. The solid blocks are still relatively lightweight, although somewhat awkward to handle by the mason. The blocks may come in various conventional block sizes, such as typically about two feet in length with various widths and heights.
In most block walls, including those formed of aerated concrete blocks, it may also be desirable to add vertical reinforcements. This may be so especially in coastal areas or other locations susceptible to high winds. For example, it may be desired to have a vertical reinforcing member, such as a reinforcing bar, periodically secured to or secured within the wall and extending from the bottom of a block wall to the top of the wall to meet certain building codes.
To provide the periodic vertical reinforcing, one conventional practice is to drill a passageway through the blocks upon completion of the entire height of the wall to receive a vertical reinforcing member. Such a process is not only awkward, but is also time consuming. Alternately, a slot may be cut into a surface of the wall to receive a vertical reinforcing member. Such, conventional ad hoc reinforcing techniques carried out at the building site may not always yield consistent results. Moreover, the time needed for such vertical reinforcing measures increases the costs of construction using conventional solid aerated concrete blocks.
In view of the foregoing background, it is therefore an object of the present invention to provide a system for making aerated concrete blocks of a type that will speed construction at the building site, and which also facilitate vertical reinforcement of walls formed from the blocks.
This and other objects, features and advantages in accordance with the present invention are provided by a system for making aerated concrete blocks having at least one passageway therein. The system may comprise a molding station for receiving materials for making aerated concrete and for allowing the materials to rise and stiffen into a body, a dividing station downstream from the molding station for dividing the body into an array of blocks, and a curing station downstream from the dividing station for curing the array of blocks. Moreover, the manufacturing system also preferably includes a drilling station downstream from the curing station to drill the at least one passageway extending through each of the blocks. The passageways provide easier grasping by the mason, reduce the weight without significantly compromising strength, and may be aligned in a wall during construction at a building site to facilitate the placement of vertical reinforcing members in the wall.
The drilling station may drill a plurality of spaced apart passageways through each block. In addition, the drilling station may include a plurality of drills, and a positioner for causing relative movement between the drills and a group of blocks to drill passageways therein. The positioner in one embodiment may grasp and move the group of blocks along a predetermined path while the plurality of drills are stationary. For example, the drills may be directed substantially vertically upward, and the predetermined path may thus be substantially vertical so that waste from drilling will fall by gravity for recycling. Accordingly, the drilling station may also further comprise a waste collection system for collecting waste from drilling.
Each drill may include a motor and a drill shaft rotatably driven thereby. In some advantageous embodiments, the motor may be an electric motor. Each drill may also include a drilling tip carried by an end of the drill shaft.
Each block may have a generally rectangular shape defining a length between opposing ends, a width between opposing sides, and a height between a top and bottom. Accordingly, the drilling station may drill the at least one passageway extending in a height direction through each block, with the at least one passageway being positioned inwardly from opposing sides and also positioned inwardly from an adjacent end. The drilling station may also drill the at least one passageway to be centered inwardly from opposing sides.
The drilling station may drill first and second passageways, each centered inwardly from opposing sides. Each first and second passageway may have an axis positioned inwardly from a respective end a distance of about one-half the width. The drilling station may further drill a third passageway extending in the height direction and being positioned between the first and second passageways, in other embodiments. This third passageway may be centered inwardly from opposing sides, and also centered inwardly from opposing ends.
The drilling station may drill each passageway to have a circular cylindrical shape, with a diameter in a range of about 1 to four inches. The length of each block may be in a range of about 16 to 24 inches, the width may be in a range of about 8 to 12 inches, and the height may be in a range of about 8 to 12 inches.
The aerated concrete block manufacturing system may also include a packaging station downstream from the drilling station to package the cured blocks for storage and transportation. The system may also include a mixing station upstream of the molding station to mix the materials prior to molding. The curing station may include an autoclave for subjecting the array of blocks to an elevated temperature and an elevated pressure for a predetermined time. In addition, a separating station may be provided between the curing and drilling stations for separating the blocks after curing.
Other aspects of the invention are directed to the drilling station as described above.